SUMMARY One of the most important causes of melanoma is exposure to ultraviolet radiation (UV). UV induces diverse changes in melanocytes, including alterations in patterns of protein synthesis, which are thought to create an environment that is favorable to melanoma formation. Recently, we and others showed that UV has a striking effect on the ?epitranscriptome,? i.e., the pattern and distribution of RNA modifications in the mRNA transcriptome. We recently found that UV exposure changes the transcriptome-wide distribution of m6A, resulting in a subset of newly synthesized mRNAs that acquire m6A in their 5?UTRs. m6A in the 5?UTR of mRNAs markedly enhances their translation. Thus, UV-induced m6A has the potential to substantially alter cellular function by enabling the synthesis of specific subsets of proteins. The goal of this study is to reveal the oncogenic role of this new mechanism of UV action, i.e., UV-mediated changes in the epitranscriptome. The specific aims of this proposal are: (1) To characterize the m6A stress response induced by UV in melanocytes. In this aim, we will use miCLIP to map UV-induced m6A sites in the transcriptome at single-nucleotide resolution. We will then determine the degree to which m6A-modified transcripts contribute to the translational response to UV using ribosome profiling in control and Mettl3-knockdown melanocytes. Overall, these experiments will define how UV globally alters the epitranscriptome in melanocytes and will define the role of m6A in the translational response to UV. (2) To determine if m6A is required for single dose UV-dependent melanoma formation. Here we will use a new murine model of melanoma in which a single UV dose markedly accelerates melanoma formation. We will examine whether UV-induced melanoma formation in vivo is affected by introducing melanocyte-specific Mettl3 deletion. These studies will provide foundational data for exploring the concept that the m6A pathway can influence melanoma development. Overall, this study will provide the critical epitranscriptomic datasets that will reveal how m6A can reprogram translation in melanocytes. The ability of UV to alter the transcriptome-wide distribution of m6A provides a compelling explanation to resolve long-standing mysteries related to how UV affects protein expression and influences melanocyte function. The experiments in these two aims will fundamentally advance our understanding of UV, cellular stress responses, melanocyte biology, and melanoma.